I found this item on Ebay a while back, and have been finding more and more of its information. This photo isn’t of the individual piece that I got (it’s from another site that had one on offer) but it’s identical.
from the seller’s description:
“Thread Counter Micrometer for Cotton, Linen, Silk and other Textile and Fabric. This brass and steel precision instrument measures the density of woven and knitted fabrics as well as wire meshes. Made in 1910 by E. V. Cook & Co. in Manchester with 5 graduated scales on rotating silver rules as follows: 1. Inch scale divided into quarters. 2. Inch scale divided into ten parts. 3. Linen measure (L). 4. French millimeter (mm). 5. French Ligne (F), a traditional unit of distance in French speaking countries, equal to 1/12 French inch (pouce). The magnifying lens ocular (X15) can be easily adjusted. The instrument comes with a leaflet with operating instruction and a box (size: 10X8X7.5 cm) lined with purple velvet.”
I’m looking forward to using this for counting the twists in tiny threads.